Completely self-driving cars that will let you sleep on the way to work are a long way off, Nissan Motor CEO Carlos Ghosn cautioned Thursday, but automatic features for parking and driving in traffic jams are around the corner.

"Self-driving cars... don't require any human intervention and remain, in my opinion, a long way from commercial reality," Ghosn told a press conference at the Foreign Correspondents' Club of Japan in Tokyo.

"They are suitable only for tightly controlled road environments at slow speeds and face a regulatory minefield."

The comments come after Ghosn said last month that self-driving cars could be on the roads by 2018 provided that regulatory obstacles were removed. In 2013, Nissan promised to have autonomous vehicles on roads by 2020.

"I want to clarify that there is a big difference between autonomous drive technology championed by Nissan, and self-driving cars. Autonomous Drive is about relieving motorists of everyday tasks, particularly in congested or long-distance situations. The driver remains in control, is at the wheel, of a car that is capable of doing more things automatically," Ghosn said.

The head of the Renault-Nissan alliance said Thursday that individual features of the group's Autonomous Drive technology will be introduced over the next four to five years.

By the end of 2016, Nissan will market a traffic jam pilot that takes care of the driving on congested highways, he said.

In the same time frame, the carmaker will make fully automated parking systems available across a wide range of vehicles. Driverless, increasingly remote parking functions for controlled settings will be available by 2019. This might allow a driver to summon her car from a parking lot, for example.

Nissan will launch "intersection autonomy," in which cars will drive through city crossroads without driver intervention, before the end of the decade, Ghosn said.

"This technological momentum in which cars will, step by step, offer more and more capability to assume journey management from drivers is a sign of things to come," Ghosn said.

Carmakers and other companies are jockeying for position in the race to produce an autonomous, mass-market vehicle that will be the first of its kind, like Toyota's Prius hybrid and Nissan's Leaf electric car.

Google, meanwhile, has taken its self-driving cars off highways and onto city streets, logging thousands of miles in Mountain View, California.

In May, the search giant unveiled a prototype self-driving car that will be part of a pilot program in California, where rules for public operation of autonomous vehicles are expected to be adopted by January.